Molecular interaction between a fragment of single-stranded DNA, contributed by a donor DNA molecule to a competent recipient cell, after a complex series of events, culminates in integration and expression of exogenous DNA sequences. The ability to bind exogenous DNA, induced during a shift to the transitory physiological state, called competence, is stimulated endogenously as well as exogenously by a small protein (competence factor, or CF) of 5 kilo dalton size. Biochemical analysis of cells undergoing competence development reveals: (1) the rate of synthesis of most of the cellular polypeptides reduces to about 10% of the normal rate and in some instances appears to be terminated; (2) the synthesis of ten new polypeptides is sequentially induced and terminated; (3) the synthesis of a new RNA transcript of high molecular weight (perhaps the message for the newly induced polypeptides) is induced and briefly maintained; (4) the rate of DNA synthesis remains unaffected. The cells return to the precompetence state of macromolecular synthesis in less than a generation: the synthesis of the normal complement of RNA and proteins is resumed; the newly induced, competence-specific polypeptides and RNA are no longer synthesized. During this "differentiated" cellular state, the cells develop the ability to bind exogenous DNA and transform. At least one of the newly induced polypeptides of 16 kilo dalton size is already implicated in the transformation process by its binding to donor DNA in presynaptic complex (single-stranded donor DNA-recipient protein complex). The specific role of other competence-specific polypeptides in affecting translocation, synapsis or integration of donor DNA is under investigation. Specifically, we will determine the specificity and stoichiometry of the formation of presynaptic complexes from purified DNA and protein components in vitro. Also, anti-PDBP antibodies will be used to study the cellular location of PDBP as well as the nature of the protein in the synaptic complex.